Glow in the dark powder.
This is strontium aluminate activated with europium. It's a very good glow-in-the-dark material, of the type you expose to light to charge up. It definitely works very nicely in that capacity, and can be charged in just a few minutes under fluorescent light. I got a sample of three different colors on eBay: The seller offers larger quantities and different formulations besides what he sells on eBay.
Not to be confused with our tritium glowing samples, which use the radioactive decay of tritium to glow for 10 or 20 years without any external input whatsoever.Source:eBay seller teddpContributor:Theodore GrayAcquired:5 September, 2002Price: $12Size: 1"Purity: <2%Sample Group:Powders

Europium oxide.
This is a white white white powder, pure as the driven snow and more powdery. I don't dare open the bottle for fear it will get on everything!

Lump.
This sample arrived with a full set of lanthanides at a time when I was missing europium, terbium, holmium, ytterbium, and of course lutetium.

This very kind donation from Max Whitby of The Red Green & Blue Company in England completed my element collection, to the extent that it gave me a plausible sample of every element one can plausibly have a sample of. (The Red Green & Blue Company is selling a periodic table collection containing similar samples of the same stuff, and if you want a ready-made collection of elements, that's the first place I would look.)

Sample from the Everest Set.
Up until the early 1990's a company in Russia sold a periodic table collection with element samples. At some point their American distributor sold off the remaining stock to a man who is now selling them on eBay. The samples (except gases) weigh about 0.25 grams each, and the whole set comes in a very nice wooden box with a printed periodic table in the lid.

Compact fluorescent bulb.
Some people complain that fluorescent light is "harsh" or "cold" or some such nonsense. The fact is, as long as you have a modern flicker-free high frequency electronic ballast such as you find in almost every compact fluorescent bulb, the light from a fluorescent bulb is far more pleasant and nature than light from an incandescent bulb. Incandescent light is dingy and yellow in comparison. It makes white walls look dirty and faded, and it comes nowhere near approximating the color of daylight, which is the gold standard against which light is judged, because daylight is what we are evolved to like.
This bulb is displayed in my Bulb Stand.Source:Hardware StoreContributor:Theodore GrayAcquired:28 November, 2003Price: $3Size: 6"Purity: <1%Sample Group:Light Bulbs

Hollow cathode lamp.
Lamps like this are available for a very wide range of elements: Click the Sample Group link below to get a list of all the elements I have lamps like this for. They are used as light sources for atomic absorption spectrometers, which detect the presence of elements by seeing whether a sample absorbs the very specific wavelengths of light associated with the electronic transitions of the given element. The lamp uses an electric arc to stimulate the element it contains to emit its characteristic wavelengths of light: The same electronic transitions are responsible for emission and absorption, so the wavelengths are the same.
In theory, each different lamp should produce a different color of light characteristic of its element. Unfortunately, the lamps all use neon as a carrier gas: You generally have to have such a carrier gas present to maintain the electric arc. Neon emits a number of very strong orange-red lines that overwhelm the color of the specific element. In a spectrometer this is no problem because you just use a prism or diffraction grating to separate the light into a spectrum, then block out the neon lines. But it does mean that they all look pretty much the same color to the naked eye.
I've listed the price of all the lamps as $20, but that's really just a rough average: I paid varying amounts at various eBay auctions for these lamps, which list for a lot more from an instrument supplier.
(Truth in photography: These lamps all look alike. I have just duplicated a photo of one of them to use for all of them, because they really do look exactly the same regardless of what element is inside. The ones listed are all ones I actually have in the collection.)Source:eBay seller heruurContributor:Theodore GrayAcquired:24 December, 2003Price: $20Size: 8"Purity: 99.9%Sample Group:Atomic Emission Lamps

Assorted glow-in-the-dark paints.
This lovely array of glow-in-the-dark (phosphorescent) powders illustrates the range of colors and the brightness of modern luminous paints. Green and aqua are europium doped strontium aluminate, the brightest of all the modern phosphorescent powders. Blue is a alkali earth silicate, while red and orange are older, noticeably less bright zinc sulfides. (The difference in brightness is so great it was difficult to get a photograph that showed the glowing of the zinc sulfide without overexposing the other colors!) The powder packets are meant to be mixed with paint, nail polish, or whatever, rendering them luminous. The bottle in the back is ready-made paint, while the small tub is a heat-and-dip powder.
This set was kindly donated by Ready Set Glo: Visit their website at www.readysetglo.com or their eBay store.
(The "purity" listed below doesn't mean a whole lot since this is a mixture of several different compounds: I'm just indicating that this sample is not a simple element but rather a mixed compound.)Source:Ready Set GloContributor:Ready Set GloAcquired:15 August, 2004Text Updated:11 August, 2007Price: DonatedSize: 4"Purity: <50%

Sample under oil.
This 5g sample under mineral oil shows the characteristic green oxide coating, as well as some shiny surfaces. Europium is notoriously difficult to keep bright, as it oxidizes in a matter of seconds if exposed to air: This is probably about as good as one can do in a bottle like this. Shinier samples would have to be in a vacuum or inert gas filled glass ampule.Source:Dave HamricContributor:Theodore GrayAcquired:20 September, 2005Price: $17Size: .75"Purity: 99.9%

I chose this sample to represent its element in my Photographic Periodic Table Poster. The sample photograph includes text exactly as it appears in the poster, which you are encouraged to buy a copy of.

Insane mineral capsules.
These minerals capsules are called "Immune Boost 77", from Morningstar Minerals. They are either being incredibly honest, or they really don't understand what they're saying when they list what amounts to nearly the entire periodic table on the label, as the "trace minerals" they contain.

Some of them are just silly, like thulium, which has absolutely no biological function. Others are a bit scarier, like thallium and thorium that are deadly poisons, and tellurium, which makes you smell of rotten onions for weeks.

Basically what they've done is list everything that occurs in even trace amounts in mixed monazite sand, which is kind of what the stuff inside looks like. The only reason they aren't seriously harmful (I assume) is that most of these are not actually present in any meaningful quantity.

My attention is drawn to these and other similar mineral supplements every time I decide to see if anything interesting has popped up on eBay for one or another of the obscure rare earths. Generally speaking if you search eBay for those guys you get very little of interest unless you turn on the option to search the text of the item description as well as the titles. Then you get lots of trace mineral supplements that one can only hope don't actually contain them.

Himalayan sea salt.
There is a list of 84 elements that seems to pop up repeatedly in the ingredient lists of "natural" mineral products, supplements, pills, and the like. Even, it turns out, in salt. Here then is the list of minerals claimed to be found in all-natural organic Himalayan sea salt:

I wish someone would tell these people that, for example, neptunium and plutonium do not occur in nature at all, let alone in salt. Unless, I suppose, if you count nuclear fallout as a "natural" source of ingredients.
What bothers me most is what this says about the level of scientific literacy, both of the people selling the stuff, and the people buying it. Does no one actually read the list? Or do they read it an not realize how preposterous it is? It's enough to make you despair for the future of mankind.
Pretty salt, though.Source:eBay seller saltwondersContributor:Theodore GrayAcquired:28 March, 2009Text Updated:4 April, 2009Price: $15Size: 0.25"Composition:NaClSbCsDyErEuGdHfHoInLaLuNdPrSmScThTlTeTbTmYbY